The present invention relates generally to the control of a work performing machine in response to the occurence of a predetermined condition with respect to a material workpiece supplied thereto.
More specifically, in the garment and associated industries, it has been generally known to utilize a sewing machine with a conventional attachment for producing a spaghetti-like tube from a bias binding strip, these tubes having external stitching which is turned inwardly by the attachment to make the stitching invisible. The attachment may be operated to produce the tube with or without an internal core. Presently, provision is made for stopping the sewing operation only in the event that the supplied bias binding strip runs out, and for this purpose switching contacts under control of the supplied binding strip are arranged to operate in a control circuit and stop the sewing machine operation, when the binding material runs out. Conventional known arrangements that are utilized to stop the machine operation only in the event that the supplied binding strip runs out, have in practice been found to be inadequate as to their scope of protection. The conventional arrangements are not arranged to stop the machine, for example, when the end seam connections between the contiguous ends of the binding strip sections are too thick, or when the binding strip may become twisted or knotted.
The present invention therefore seeks to provide a unique control switch which will extend the scope of protection and stop the machine operation in those above enumerated situations in which the presently known controls are ineffective. For such purpose, a rocker type switch structure in the nature of a single-pole double-throw switch is utilized, this switch being provided with a hinged rocker arm which is normally biased in one direction to a throw position that operatively closes a first set of contacts, and upon hinged removement of the rocker arm in an opposite direction will operate to open the first set of contacts and close a second set of contacts. The first and second sets of contacts are electrically connected in parallel in a control circuit in such a manner that the closure of either set of contacts will function to stop the machine operation. Normally, the biasing strip-material is fed to the machine attachment between the first set of contacts and serves to maintain these contacts in an open position. The second set of contacts are adjustable so that, during such normal operation, the second set of contacts will also occupy an open position. As thus arranged, if the supplied binding strip should break or run out the first set of contacts will close and stop the machine operation. If the seams connecting the ends of the binding strip sections are too thick, or if the binding strip should become twisted or knotted, then the second set of contacts will close and stop the machine operation.